April, 1915. 



KNOWLEDGE. 



119 



CONDENSATION OF THORIUM AND RADIUM 

 EMANATIONS.— In The Philosophical Magazine for March 

 the present writer also contributes a paper on the condensa- 

 tion of these two emanations. The object of the research 

 was to find out whether isotopes had or had not the same 

 temperature of condensation. It was found that in a 

 mixture of the two emanations at atmospheric pressure, 

 thorium emanation appeared to be condensed before radium 

 emanation ; while, if the experiment was made in a vacuum, 

 the reverse was the case. From theoretical considerations 

 it was shown that results of this nature are to be ex- 

 pected, even if individual atoms of each emanation had 

 identical condensation points. The difference in behaviour 

 is in all probability due to the different periods of 

 average life. Indirect evidence was obtained in one ex- 

 periment that the two emanations behaved identically in 

 respect to their condensation and volatilisation. 



By altering the external conditions the condensation 

 point of either emanation can be varied between — 150° C. 

 and - 185° C. 



RELATION BETWEEN X-RAY WAVE-LENGTHS 

 AND ABSORPTION.— A paper on this subject, by Pro- 

 fessor W. H. Bragg, appears in The Philosophical Magazine 

 for March. It deals with the absorption of rays emitted by 

 substances when these are bombarded with cathode or 

 .r-rays. It is well known that secondary rays are of two 

 types, and are characteristic of individual elements. The 

 main conclusion reached is that it is probable that " the 

 characteristic rays of a substance form a system which 

 can only be excited as a whole." In the meantime this 

 result has been proved to be correct for some six or so 

 elements ; if, however, further work enables it to be 

 stated in a generalised form applicable to all the elements, 

 an important step will have been made in our knowledge, 

 not only of the material, using the word in its widest sense, 

 inside an atom, but also of how that material is held 

 together. 



ZOOLOGY. 



By Professor J. Arthur Thomson, M.A., LL.D. 



RELATIVE LENGTHS OF OUR TOES.— Onera A. 

 Merritt Hawkes finds that there are three types of feet, of 

 which two are common. The first or great toe may project 

 beyond all the others (L type). The second toe may pro- 

 trude, not only beyond the third, fourth, and fifth, but also 

 beyond the first (S type). This is much less common than 

 L. The first and second toes are of the same length, and 

 longer than the others (E type). This is very unusual. 

 There is some limitation in regard to sex, the S type occur- 

 ring more commonly in females than in males. As the 

 S type is commonest in the foetus, it may be said that 

 in this, as in some other features, woman is a more youth- 

 ful type than man. In inheritance the L type is irregularly 

 dominant over the S type of foot. 



PHEASANTS AND MUTATION.— Mr. C. William 

 Beebe, the Curator of Birds to the New York Zoological 

 Society, has been studying pheasants for some years, and 

 his opinion on the factors of evolution is well worth having. 

 He says that he began with some prejudice against the 

 " mutation theory " (of brusque, discontinuous, or saltatory 

 variations), but that the more he observed such species as 

 the golden and Amherst pheasants (Chrysolophus piclus 

 and amhersiiae), the colour relations in both sexes, and the 

 results of hybridism, the more necessary some such phe- 

 nomena as saltations appeared to be in these particular 

 instances. The genus Phasianus seems to afford good 

 illustrations of continuous variation, and the genus 

 Euplocomus of saltatory variations. Both forms have been 

 operative in nature. 



CROCODILE'S NEST.— Mr. \V. Schultze, of the Bio- 

 logical Laboratory at Manila, describes the nest of a 



crocodile (Crocodilus paluslris) near Taytay, Palawan. A 

 peculiar mound of grass on the shore of a lake attracted 

 attention, and it was found to be a crocodile's nest. A 

 space about eight metres long and five metres wide had 

 been cleared of the coarse, wiry grass {Ischaemum) which 

 grew there, and a mound had been made 2-5 metres in 

 diameter at the base and 1-5 metres in height. The grass 

 was mixed with sand, and was moist. About the centre 

 of the mound there were thirty eggs in several layers. The 

 egg is oblong ellipsoidal, with a very hard porous shell, 

 a high porcelain lustre, and a strongly marked opaque 

 white band around the middle (girth). It was found that 

 the time of incubation in the Philippines is between seven- 

 teen and eighteen weeks. 



HOW A STING -RAY PROTECTS ITS EYE.— It is 

 well known that the eyes of fishes are lidless, and cannot be 

 closed like those of most higher vertebrates. Sometimes, 

 however, they are well protected from injury, and B. Sun- 

 dara Raj gives a good example in Trygon kuhlii, one of the 

 sting-rays. It lies buried in the sand with the eyes, the 

 spiracles, and a portion of the formidable spined tail pro- 

 jecting. If sand or other particles be dropped down, the 

 upper margin of the spiracle nearest the eye forms a pro- 

 jecting fold which serves both to protect the eye and to 

 exclude foreign objects from the spiracle. 



SIZES OF RED BLOOD CORPUSCLES.— An interest- 

 ing suggestion has been made by Dr. J. Burton Cleland 

 that specialisation is attended with a reduction of the size 

 of the red blood cells. Thus, among fishes, those of Ceratodus 

 are 39 x 23 to 25/i, which is " cumbersome " ; those of 

 Elasmobranchs vary from 18 x 12-5 to 23 x 13 -5m : those 

 of Teleosteans range from 9x7 to 13-5 x 10-3m- In 

 Therapion unicolor they are almost spherical, 6 to 8^- 

 Similarly in birds the Emu has 15-5 to 16-5x8-5 to 9-S^i ; 

 the Grebes, Penguins, Herons, Pelicans, and the like have 

 approximately 1 4 x 8/i ; in Passerine birds (except Cor- 

 vidae) there is a definite tendency to smaller cells, 10 to 

 12x5 to7 M . 



STINGS OF JELL YFISHES— The stinging threads of 

 the common jellyfish (Aurelia aurita) are not strong enough 

 to pierce the ordinary human skin, but bathers on British 

 coasts have sometimes painful experience of the virulence 

 of the orange or the blue species of Cyanea. In other waters 

 there are much more formidable jellyfishes. Thus Mr. 

 S. F. Light, in describing Philippine medusae, notes of 

 Chiropsaimus qiiadrigatus that the sting of the tentacles 

 is very dangerous. Swelling and inflammation begin almost 

 immediately, blisters form, the heart action is impaired, 

 respiratory spasms and nervous twitchings of the muscles 

 ensue, and there is intense general pain. The natives of 

 Palawan reported that the sting may be fatal. Another 

 dangerous form is Daciylometra quinquecirrha, which causes 

 severe poisoning. The native remedy is sugar solution 

 taken internally and applications of vinegar externally. 



NESTS OF FALSE SCORPIONS— A very fine piece of 

 observational work has been done by Mr. II. Wallis Kew, who 

 has for the first time described the whole process of nest- 

 making in the little creatures known as false scorpions, or 

 pseudoscorpions, which are moderately well represented in 

 Britain. Nests are made by all individuals of both 

 for moulting, for brood purposes, and sometimes for 

 hibernation, The interior is lined with dense spun tissue, 

 almost like silk paper, which takes days or even weeks to 

 make. There may be an external covering of earthy or 

 ible m.itt rials attached by silk. The silk is formed by 

 glands in the cephalothorax, and is conveyed by dm 

 the tips of the chelii erae, or first pair of appendages. The 

 silk is drawn out in separate viscid threads, which may 

 coalesce or remain separate. There are five or six from each 

 chelicera, but these may form one. The spinning is asso- 

 ciated with continuous forward and backward movements 

 of the body, and with lateral movements of the cheliccrae. 



